1. Field of the Invention
This invention relates to new polymeric cationic dyes for use in the coloring, surface dyeing, inking or printing of substrates such as paper, fiber, leather and the like. The invention also relates to a process for dyeing paper with said new dyes and to paper dyed therewith.
2. Description of the Prior Art
A variety of cationic dyes have been employed for the dyeing of paper, pulp or the like. However, these cationic dyes generally suffer from the disadvantages of considerable loss in tinctorial strength when applied to the materials such as paper and pulp, with the result that the materials are not deeply dyed and a large amount of dyes not fixed on the materials remains in the waste water after dyeing the materials, which leads to environmental problems of water pollution and the like.
On one hand, dyes are shifting to liquid products in recent years for reasons of easiness of handling and removal of dust pollution. However, cationic dyes are of poor storage stability at temperatures and times encountered in formation of dyes into liquid, as compared to other types of dyes and suffer undesirable phenomena such as a lowering of concentration, change of color, occurrence of an insoluble material, etc. due to storage. In particular, the pollution arising from the waste water as mentioned above is in serious problem to a dyeing factory. Now, a variety of dyeing assistants are often used to enhance tinctorial strength of dyes. However, this approach provides increased cost and fails to achieve a desired effect. In view of this problem, basic dyes have been proposed in U.S. Pat. No. 4,323,362. The dyes are stated to possess good substantivity on paper and to alleviate environmental problems relating to the discharge of the waste water after dyeing paper. However, those dyes are not satisfactory for deep dyeing and do not have tinctorial strength enough to cope with a reduction in dyeing time, simplification of dyeing equipment, etc. which bring about a reduction in dyeing cost.